package Lab5;
/**
 * 实验 5 
 * 问题 1. 编程实现文件合并和去重操作。
 */
import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;


public class Lab5P01 {
    /**
     * @param args
     * 对A,B两个文件进行合并，并剔除其中重复的内容，得到一个新的输出文件C
     */
    //重载map函数，直接将输入中的value复制到输出数据的key上
    public static class Map extends Mapper<Object, Text, Text, Text>{
        private static Text text = new Text();
        public void map(Object key, Text value, Context context) throws IOException,InterruptedException{
            text = value;
            context.write(text, new Text(""));
        }
    }

    //重载reduce函数，直接将输入中的key复制到输出数据的key上
    public static class Reduce extends Reducer<Text, Text, Text, Text>{
        public void reduce(Text key, Iterable<Text> values, Context context ) throws IOException,InterruptedException{
            context.write(key, new Text(""));
        }
    }

    public static void main(String[] args) throws Exception {
        // TODO Auto-generated method stub
        Configuration conf = new Configuration();
        conf.set("fs.default.name","hdfs://localhost:9000");
        String[] otherArgs = new String[]{"input","output"}; /* 直接设置输入参数 */
        if (otherArgs.length != 2) {
            System.err.println("Usage: wordcount <in><out>");
            System.exit(2);
            }
        Job job = Job.getInstance(conf,"Merge and duplicate removal");
        job.setJarByClass(Lab5P01.class);
        job.setMapperClass(Map.class);
        job.setCombinerClass(Reduce.class);
        job.setReducerClass(Reduce.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(Text.class);
        FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
        FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
        System.exit(job.waitForCompletion(true) ? 0 : 1);
    }
}
